At present, in a financial bill processing device, a thickness sensor, a magnetic sensor, an ultraviolet sensor, an infrared sensor, a touch image sensor or the like which may be adopted in an existing bill recognition module cannot rapidly recognize a softness degree of a bill with a small amount of information. Even the touch image sensor with a high definition can only distinguish between new bills and old bills. In practical applications, many new bills become soft due to moisture and the like, thereby affecting normal usage and circulation of the bills. The existing touch image sensor cannot recognize such soft new bills. In another existing recognition method, such soft bills are recognized by means of sounds. However, accuracy and stability of the recognition with sound are seriously affected by noises in various changeable frequencies generated by the machine itself and the surroundings.